A chemical amplification resist composition is a pattern forming material of forming a pattern on a substrate by producing an acid in the exposed area upon irradiation with an actinic ray or radiation such as far ultraviolet light and through a reaction using the acid as a catalyst, changing the developer solubility of the area irradiated with an actinic ray or radiation and that of the non-irradiated area.
In the case of using a KrF excimer laser as the exposure light source, a resin having small absorption in the region of 248 nm and having a basic skeleton of poly(hydroxystyrene) is primarily used as the main component and therefore, this is an excellent system capable of forming a good pattern with high sensitivity and high resolution compared with conventional naphthoquinonediazide/novolak resin systems.
On the other hand, in the case of using a light source of emitting light at a shorter wavelength, for example, in using an ArF excimer laser (193 nm) as the exposure light source, a satisfactory pattern cannot be formed even by the above-described chemical amplification system, because the compound having an aromatic group substantially has large absorption in the region of 193 nm.
In order to solve this problem, a resist containing a resin having an alicyclic hydrocarbon structure has been developed for the use with an ArF excimer laser.
Various improvements are being made also to the acid-decomposable resin that is a main constituent component of the chemical amplification resist composition, and a specific acid-decomposable resin is disclosed, for example, in Non-Patent Documents 1 and 2.
Furthermore, various improvements are being made also to the resin having a lactone structure, and a resin having a specific lactone structure is disclosed, for example, in Patent Document 1.
However, at the formation of a fine pattern having a line width of 100 nm or less, it is required to improve not only resolution but also performance in terms of line edge roughness of a line pattern.
The line edge roughness as used herein means that the resist edge at the interface between the line pattern and the substrate irregularly fluctuates in the direction perpendicular to the line direction due to resist characteristics and when the pattern is observed from right above, the edge gives an uneven appearance (approximately from ±several nm to ±several tens of nm). The unevenness is transferred to the substrate through an etching step and when the unevenness is large, this causes deterioration of electrical properties and reduction in the yield.    Non-Patent Document 1: Polymer 43, (2002) 1963-1967    Non-Patent Document 2: The International Society of Optical Engineering, Proceedings of SPIE, 110-119 (2002)    Patent Document 1: JP-A-2001-33971 (the term “JP-A” as used herein means an “unexamined published Japanese patent application”)